The role of antimony compositions in the flameproofing of various polymers has been known for many years. One problem associated with many of the prior art antimony compositions used in flameproofing systems is the delustering of fibrous polymers. This problem may be overcome by providing an antimony composition of sufficiently small particle size, significantly less than one micron, so that the particles do not scatter light and thus do not deluster the treated polymer.
Another difficulty associated with the use of an antimony composition in flameproofing polymers lies in the incorporation of the antimony compositions in the polymer. It is desirable to mix the antimony composition with a solution of the polymer in a polar organic spinning or casting solvent prior to final product fabrication. Many prior art compositions of antimony are neither soluble nor readily dispersible in the polar organic solvents commonly used in polymer formulations.
Several methods for preparing colloidal dispersions of antimony pentoxide for use as flameproofing agents for plastics, fibers, elastomers and other polymeric compositions are known in the art. For example, U.S. Pat. No. 3,860,523 teaches a method for forming collodial antimony pentoxide by deionizing potassium antimonate with a cation exchange resin. Another method for forming sols of antimony pentoxide is shown by U.S. Pat. No. 3,657,179 which teaches the use of antimony trichloride and nitric acid to form a dispersion in a polar organic solvent, and stabilization of the dispersion with an alpha-hydroxy carboxylic acid. The dispersions taught by the U.S. Pat. No. 3,657,179 contain from 0.01% to 5% water by weight.
The formation of pentavalent antimony compositions by the oxidation of trivalent antimony compositions with hydrogen peroxide is also known in the art. U.S. Pat. No. 3,836,557 shows a method for preparing water soluble salts of pentavalent antimony glycol esters by reacting antimony trioxide with hydrogen peroxide in ethylene glycol under vacuum to remove the water of reaction. U.S. Pat. No. 3,676,477 teaches the formation of pentavalent antimony esters by reacting antimony trioxide with hydrogen peroxide in a polyhydroxy alcohol with distillation to remove the water of reaction.
Many of the foregoing methods require expensive procedures for formulating compositions which can be employed effectively in relatively few polymer systems.
It is therefore an object of this invention to provide a stable dispersion of hydrous antimony pentoxide and a process for making said dispersion.
Another object of this invention is to provide hydrous antimony pentoxide sols which can be employed as flame retardant agents in natural and synthetic fibers and other polymeric materials, and a process for making said sols.
A further object of this invention is to provide an economical process for making hydrous antimony pentoxide sols from commercial grades of antimony trioxide.
Other objects of this invention will become readily apparent from the following description of the invention.